By 1974, Gilligan's Island was well established in syndication, and in my home district, having been introduced to cable just a year earlier, viewers could see the show twice a day most days.
Creator Sherwood Schwartz, having seen The Brady Kids fall apart in its 2nd season, leading to cancellation, decided it was time to bring Gilligan and the rest of the castaways back. However, not all of the cast reunited for The New Adventures of Gilligan, which replaced Brady Kids on ABC's Saturday schedule. TVSeriesFinale.com uploaded the open & close to YouTube:
As it has been explained, Tina Louise wanted nothing further to do with the franchise, wary of typecasting, and Dawn Wells (Mary Ann) was away with a touring theatre company and could not return. Filmation's stalwart female voice artist, Jane Webb, voiced both Ginger & Mary Ann, credited as "Jane Edwards" for the latter part. Wells would turn the same trick when the gang got back together 8 years later for Gilligan's Planet, back on their original network, CBS. If anything at all, the most experienced voice actor in the group was Jim Backus (Mr. Magoo), who for all we know might have doubled as an uncredited voice coach. New Adventures would move to Sundays for its 2nd & final season while Bob Denver (Gilligan) moved on to the Kroffts' Far Out Space Nuts back on CBS. Devotees of the Gilligan franchise hoping for a DVD release may have to petition Warner Bros., which holds the rights. Right now, even though New Adventures marked its 35th anniversary last year, it doesn't seem likely. WB, after all, has a whole treasure trove to go through.
New Adventures of Gilligan tried to recapture the spirit of the original series, but couldn't find enough viewers. Filmation actually did themselves in, since CBS booked another of their freshman entries, Shazam!, directly opposite New Adventures. Enough said.